Did this a lot in the 80s. We'd moved away from Boro and were living near Huddersfield so there were lots of easily accessible away games that I went to with my dad. Always in with the home fans as it was much easier for getting away and back home, especially as we neither needed nor wanted to get escorted back to the train station. Who recalls the way away fans were policed back then eh? Not nice.
Can't even remember everywhere we went, but definitely Leeds, Huddersfield, Bradford, Barnsley, both Sheffield, both Manchester, Bury, Burnley, Bolton, Rochdale, Rotherham, Doncaster, Chesterfield, Oldham (brrrr!).
Elland Road by some distance the most unpleasant, a truly awful experience, and always accompanied by an atrocious result.
Barnsley definitely the best, never even had to pretend to be anything other than a Boro fan there. Favourite was (I think) a 3-0 win towards the end of the 87/88 promotion season - Tykes more than happy to chat and express approval at how good we were that day.